The W 25 was the original Silver Arrow. Originally painted white, it arrived at the Nürburgring for its first race one kilogram too heavy for the 750-kg (1,650-pound) formula. The mechanics sanded down the paintwork in order to reduce its weight, exposing the bare, shining silver color of its body. Suitably relieved, the team was able to line up at the start with the W 25. The car went on to win the race and later picked up its nickname Silver Arrow.

• Cylinders 8
• Displacement 205 cu in
• Output 354 hp (260 kW)
• at engine speed 5800/min
• Top speed 175 mph